1. Field of the Invention
The present invention relates to devices for preventing the accumulation of ice in low temperature refrigeration devices. More particularly, the invention relates to heating devices for facilitating the removal of accumulated ice from the doors and corresponding closure surfaces of low temperature refrigeration devices, including ultra-low temperature freezers.
2. Description of the Prior Art
Low temperature refrigeration devices, especially ultra-low freezers, are commonly used in laboratory settings for storing biological samples. These freezers typically operate between approximately -40.degree. C. and -95.degree. C., and can develop substantial ice build-up around the door seal and closure surfaces depending on frequency of entry, ambient temperature, and humidity conditions. The accumulated ice can have seriously debilitating affects on freezer performance, including interfering with proper door sealing and interior accessibility, and overloading the door latching and mounting mechanisms. Even moderate amounts of ice build-up can so interfere with proper sealing that the required interior temperature cannot be maintained or can only be maintained by overworking the cooling mechanism. When this happens, valuable, perhaps irreplaceable, freezer's contents may be damaged by thawing.
A well-known method of de-icing involves allowing the built-up ice to thaw naturally. This inconveniently entails removing the entire contents of the iced freezer to a second freezer, and waiting for the ice to thaw. Any attempt to artificially hasten thawing, including prying the ice loose, pouring hot water on the ice, or placing space heaters nearby, can damage the door seals or other components of the freezer unit.